Radial sliding-contact bearing for rotary rolls

ABSTRACT

A radial sliding-contact bearing for rotary rolls has a cylindric fixed inner portion (2), a sleeve (4) rotatable thereon, and a gap (6) between the sleeve and the inner portion intended for a water film which in operation forms a rotary bearing for the sleeve. On its peripheral surface the inner portion has recesses (8&#39;) for facilitating an even distribution of the water over the surface of the inner portion (2) in operation. The water is fed to the gap (6) through first and second longitudinal rows of nozzle openings (14, 16) in the peripheral surface of the inner portion (2), which are connected to a common water supply channel (18) in the inner of the inner portion. As seen in the rotational direction of the sleeve, the nozzle openings, more particularly, end in the periphery of the inner portion before and behind, respectively, a longitudinal surface groove (8&#39;) in the upper side of the inner portion, said surface groove (8&#39;) serving for conveying on water coming from the first row of openings ( 14) and forming part of said recesses. The openings (16) in the second row, which is located before the area of the horizontal radial plane of the sleeve, have a water outlet direction (26) with a not unessential resultant in said rotational direction (24).

TECHNICAL AREA

The present invention relates to a radial sliding contact bearing forrotary rolls, with a cylindric fixed inner portion, a sleeve rotatablethereon, and a gap intended for a fluid film arranged between the sleeveand the inner portion, said film in operation forming a rotationalbearing for the sleeve, the fluid being delivered to the gap throughfirst and second longitudinal rows of nozzle openings in the peripheralsurface of the inner portion, said rows being arranged on each its sideof a vertical diametrical plane through the inner portion.

PRIOR ART

A bearing of this kind is known through U.S. Pat. No. 4,558,960. Thisbearing is practically used in a roll assembly with curved roll intendedto be used e.g. as a transport roll or treatment roll within the paperor textile industry. The roll is assembled from sleeve modules connectedtogether end-to-end sealingly and torque transmitting, said modulesconsisting of rotatable sleeves of the kind defined by way ofintroduction. This roll rotates about a fixed shaft assembled fromcylindric modules arranged end to end and consisting of inner portionsof the kind likewise defined by way of introduction, each sleeve thenrotating around a corresponding cylindric module. More particularly, thecylindric modules/inner portions have somewhat inclined end surfaces andare arranged end to end with the end surfaces suitably orientated togive the roll the desired curved shape. A steel rod passing through thecylindric modules is tensioned and attached at the ends for obtaining arigid shaft body.

The said recesses in the peripheral surface of the inner portion includea number of axially extending surface grooves distributed around theperiphery of the shaft body, and transverse grooves connecting togethersaid surface grooves, as well as trapezoidally shaped shallow pocketswhich at their broader base pass over into the longitudinal grooves.Water for the water film appearing during operation is delivered at oneend of the longitudinal grooves and is withdrawn at the other one.

Although the introduction of radial bearings and rolls of the describedtype meant an improvement within the art in a number of respects, somedisadvantages have also been noted in practice. Due the absence of awater film between the upper bearing surfaces during standing still ofthe bearing the roll has thus turned out to be very slow and powerdemanding at start. Also in operation seemingly unwarranted increases ofthe power demand and unexplainable wear of portions of the bearingsurfaces have appeared.

Through U.S. Pat. No. 3,386,149 a radial bearing for rotating rolls isknown, in which two rows of radially directed openings extend throughthe wall of a tube shaped fixed shaft on equal distances from thevertical central line through the shaft. On this shaft the roll isarranged as a rotatable sleeve. A liquid under pressure is introducedthrough the tube shaped shaft to the radial openings and out into gapbetween the shaft and the sleeve. The radial liquid jets flowing outthrough the openings in the gap are stated to form two lines of supportfor the sleeve in order to facilitate starting of the sleeve fromstanding still and as a support against an applied load in the form of aweb transported over the sleeve.

THE INVENTION

The object of the present invention is to provide a bearing requiringless power than thus far both at start and during operation.

According to the invention this object is attained in that, at a bearingof the kind defined by a way of introduction,

the two rows of nozzle openings communicate with each other via a commonfluid delivery channel in the inner of the inner portion,

the openings of the first row are so located with respect to thevertical diametrical plane that, on the one hand, at start, fluidflowing out through these into the gap lifts the sleeve from the innerportion, and on the other hand, due to tangential forces appearingduring start and in operation, said first openings will be choked by therotatable sleeve resulting in a fluid increase at the openings of thesecond row,

the openings in the second row, which is located before the area of thehorizontal radial plane of the sleeve, have a fluid outlet directionwith a not unessential resultant in the rotational direction, so thatfluid flowing out therefrom due to said fluid pressure increasecounteracts tilting movement of the sleeve against the inner portionprovoked by a force of reaction appearing due to said tangential force,

the two opening rows furthermore being so arranged with respect to eachother that in operation the tangential force and its force of reactionare kept in a dynamic balance and thereby frictional forces between thesleeve and the inner portion are minimized.

At start the direct water supply under pressure through the nozzle rowsalong the full length of the roll lifts the roll assembled from thesleeves without delay from the fixed shaft assembled from the cylindricinner portions so that the roll can be started with a very smallstarting power as compared with that possible with a roll with a bearingaccording to U.S. Pat. No. 4,558,960. Furthermore, however, also aconspicuous and unexpectedly great decrease of the required power duringoperation of the roll is obtained. As an example it can be mentionedthat where a roll assembly with a bearing according to U.S. Pat. No.4,558,960 requires a power of 18 kW at a roll speed of 1000 n/m, thesame assembly modified with a bearing arrangement in accordance to theinvention has turned out to require a power of only 4 kW at the samespeed.

A likely model of explanation is that at the known roll assembly thetangential forces appearing due to a load tend primarily to press thesleeve against the inner portion within a first area of the latterlocated before the vertical radial plane thereof. As a reaction on thisforce action the sleeve is subjected to a tilting movement which despitethe water film brings it to a friction increasing contact with the innerportion within a second area of the inner portion located behind thevertical radial plane essentially in the vicinity of the horizontalradial plane of the inner portion. Investigations of the wear patternafterwards in a radial bearing according to U.S. Pat. No. 4,558,960 haveshown wear primarily in the second area.

In the bearing according to the invention the first opening row islocated in the first area and the second opening row before the secondarea. When the sleeve, due to the tangential forces in accordance withthe above is pressed in a direction against the first area the gap overthe first openings is decreased which thereby become a tendency to bechoked. Since the two opening rows communicate, the pressure at thesecond openings is increased and a greater flow of water flows out therein a direction towards the second area due to the slope of theseopenings in a direction thereto. This greater flow of water counteractsthe above discussed tilting movement of the sleeve to such a degree thatthe sleeve does not come into friction increasing with the inner portionwithin the second area. In operation there is balance between thepressure at the two opening rows, the first opening row then essentiallyonly having as its function to feed water to the water film of theradial bearing and the second opening row essentially only having acontrolling function on the movement of the sleeve.

DESCRIPTION OF THE FIGURES

An embodiment of the invention shall now be described more closely withreference to the attached drawings, on which

FIG. 1 in perspective shows the cylindric inner portion of the radialbearing according to the invention, and

FIG. 2 shows a portion of a radial section along the dashed doted lineII in FIG. 1, an associated portion of a sleeve rotating around theinner portion being also shown.

PREFERRED EMBODIMENT

The radial sliding-contact bearing according to the inventionillustrated on the drawing, of which mainly only essential portions areshown on the drawing, has a cylindric fixed inner portion 2. On theinner portion 2 a sleeve 4 (left out in FIG. 1 for the sake ofclearness) is rotatably arranged. Between the sleeve 4 and the innerportion 2 there is a gap 6 intended for a water film which in operationforms a rotational bearing for the sleeve. The inner portion on itsperipheral surface has recesses which shall facilitate an evendistribution of the water over the surface of the inner portion duringoperation. The recesses can include a number of axially extendingsurface grooves 8 distributed around the periphery of the shaft body,and transverse grooves 10 connecting together said surface grooves, aswell as trapezoidally shaped shallow pockets 12 which at their broaderbase passes over into the longitudinal grooves 8.

The details of the bearing described thus far correspond tocorresponding details of the bearing according to U.S. Pat. No.4,558,960.

Contrary to this known bearing, however, water is fed to the gap 6through first and second longitudinal rows of nozzle openings 14 and 16,respectively, in the peripheral surface of the inner portion 2, whichare connected to a common water supply channel 18 in the inner of theinner portion through channels 20 and 22, respectively. For relating thelocation of the nozzle openings to the system of recesses 8, 10, 12 inthe peripheral surface of the inner portion, vertical and horizontalradial planes in an imagined operational position of the bearing havebeen indicated in the Figures with dashed lines A and B, respectively.As seen in the rotational direction of the sleeve, designated 24 in FIG.1, the openings 14 and 16, respectively, in the periphery of the innerportion end before and behind, respectively, one of the longitudinalsurface grooves, here designated 8, for the sake of clearness. Theopenings 16 in the second row are generally located before the area ofthe horizontal radial plane B of the sleeve - more particularly beforethe next longitudinal surface groove 8 in the embodiment shown. Thechannels 22 and thereby the water outlet direction of the openings 16,indicated with an arrow 26 in FIG. 2, extend under a direction with anot unessential resultant in the rotational direction 24, i.e. thedirection 26 deviates considerably from an imagined radius passingthrough the opening 16.

In the described bearing according to the invention the row of openings14 is located in a first area of the inner portion 2, against which thesleeve 4 in operation has a tendency to come into contact under theinfluence of tangential forces provoked by the rotation of the sleeve 4.The row of the openings 16 is located before a second area of the innerportion 2, against which the sleeve 4 as a reaction to the justmentioned movement of the sleeve has a tendency to tilt. In FIG. I thesecond area may be imagined to be located generally between two surfacegrooves 8 following after the groove 8,, and in any case before thehorizontal radial plane B. When the sleeve due to the tangential forcesin accordance with the above is pressed in a direction against the firstsurface area the gap over the openings 14 is decreased, said openingsthereby becoming a tendency to be choked. Since the two opening rowscommunicate via the channels 20, 22 the pressure is increased at theopenings 16 and a greater water flow there flows out into the gap 6 inthe direction 26 towards the above mentioned second area. This greaterflow of water counteracts the above discussed tilting movement of thesleeve 4 to such a degree that the sleeve does not come into frictionincreasing contact with the inner portion 2 within the second surfacearea. In operation there is a balance between the pressures at the twoopening rows, the first opening row 14 essentially only having as itsfunction to feed water to the water film of the radial bearing and thesecond opening row 16 essentially only having a controlling function onthe movement of the sleeve 4.

In a way conventional per se the bearing according to the invention canbe used at a roll assembly with a curved roll intended to be used e.g.as a transport roll or treatment roll within the paper or textileindustry. The roll is assembled by end-to-end sealingly and torquetransferring connected sleeve modules, consisting of the sleeves 4. Thisroll rotates about a fixed shaft assembled from cylindrical modulesarranged end-to-end, consisting of the inner portions 2, each sleeve 4then rotating around a corresponding cylindrical module 2. Moreparticularly, the cylindric modules/inner portions 2 have somewhatinclined end surfaces and are arranged end-to-end with the end surfacessuitably orientated for imparting to the roll the desired curved shape.A steel rod passing through the cylindric modules is tensioned andattached at the ends so as to obtain a rigid shaft body. For makingpossible the said orientation of the inner portions 2 a pair of holerows 14 and 16, respectively, can exist in association with every secondone of the surface grooves 8, only one such pair at the time then, ofcourse, acting during operation, i.e. the pair which for the time being,depending upon the actual orientation of the inner portion, is locatedin association with the upper side of the inner portion 2, as is shownin FIG. 2.

For making possible reversed rotational direction, should the needoccur, the two rows of openings 14 and 16, respectively, can be locatedessentially mirror like with respect to the surface groove 8'.

We claim:
 1. Radial sliding-contact bearing for rotary rolls, with acylindric fixed inner portion (2), a sleeve (4) rotatable thereon, and agap (6) intended for a fluid film arranged between the sleeve and theinner portion, said film in operation forming a rotational bearing forthe sleeve, the fluid being delivered to the gap (6) through first andsecond longitudinal rows of nozzle openings (14,16) in the peripheralsurface of the inner portion (2), said rows being arranged on each itsside of a vertical diametrical plane (A) through the inner portion,characterized in thatthe two rows (14,16) of nozzle openings communicatewith each other via a common fluid delivery channel (18) in the inner ofthe inner portion (2), the openings of the first row (14) are so locatedwith respect to the vertical diametrical plane that, on the one hand, atstart, fluid flowing out through these into the gap (6) lifts the sleeve(4) from the inner portion (2), and on the other hand, due to tangentialforces appearing during start and in operation, said first openings (14)will be choked by the rotatable sleeve (4) resulting in a fluid increaseat the openings of the second row, the openings (16) in the second row,which is located before the area of the horizontal radial plane (B) ofthe sleeve, have a fluid outlet direction (26) with a not unessentialresultant in the rotational direction, so that fluid flowing outtherefrom due to said fluid pressure increase counteracts tiltingmovement of the sleeve against the inner portion provoked by a force ofreaction appearing due to said tangential force, and the two openingrows (14,16) furthermore being so arranged with respect to each otherthat in operation the tangential force and its force of reaction arekept in a dynamic balance and thereby frictional forces between thesleeve (4) and the inner portion (2) are minimized.
 2. Radialsliding-contact bearing according to claim 1, characterized in that thefirst and second longitudinal rows of nozzle openings (14 and 16,respectively) end, as seen in the rotational direction of the sleeve, inthe periphery of the inner portion before and behind, respectively, of alongitudinal surface groove (8') in the upper side of the inner portion,said surface groove (8') serving for conveying on fluid coming from thefirst row of openings (14) and forms part of recesses (8,10,12) in thesurface of the inner portion arranged for the same purpose.
 3. Radialsliding-contact bearing according to claim 2, characterized in that, formaking possible reversed rotational direction if desired, the two rowsof openings (14, 16) are located essentially mirror like with respect tothe surface groove (8').
 4. Radial sliding-contact bearing according toclaim 2 or 3, characterized in that the inner portion (2) around itsperiphery has at least two sets of first and second nozzle openings (14and 16, respectively) in association with a corresponding longitudinalsurface groove (8').